PARENT SESSION
Oral Session #64: Plant Population Ecology.
Presiding: S. Collins
Wednesday, August 7. 1:00 PM to 4:45 PM. Gila Meeting Room, TCC.

Masting by chance or necessity: the reproductive variability of plant populations in stochasitc environments .

Kerkhoff, Andrew^*,1, ¹ University of New Mexico, Albuquerque

ABSTRACT- Masting is the synchronous, episodic production of large seed crops by perennial plant populations. Generally, hypotheses concerning the evolutionary origin and maintenance of masting entail economies of scale, where the benefit of large, synchronous reproductive events accrues by overcoming some environmental constraint, such as pollen limitation or seed predation. Because all perennial plants face some degree of interannual environmental variability, assessing the importance of economies of scale selection requires a clear expectation for the reproductive dynamics of plants adapted to variable environments. Using a dynamic life-history model, I demonstrate that the fundamental patterns associated with masting should be expected for a population of plants utilizing optimal allocation strategies, even in the absence of economies of scale dynamics. Thus, benefits realized via economies of scale can be seen as epiphenomena of life-history evolution in even modestly variable environments. As variations on an established evolutionary theme, economies of scale undoubtedly provide selective advantages. However, caution should be exercised when inferring them as the major ecological and evolutionary determinant of reproductive variability of plant populations.

KEY WORDS: proximate vs. ultimate explanation, optimal life-histories, population variability and synchrony, stochastic dynamic models